Heat treating



Nov. 28, 1944.

D. H; MONTGOMERY HEAT TREATING Filed Feb. 18, 1942 INVENTOR 00mm h.uoyraauzev ATTORNEYS Patented Nov. 28, 1944 UNITED STATE s PATENToi-Pica y I nga'r'ranamd Donald H. Montgomery, West Hartford, Conn; as:

sis-nor to The New Britain Machine Com New Britain, Conn., a corporationor Connecticut Application February 18, 1942, Serial No. 431,311 1Claim. 7 ('Cl. 148-10) form a protective coating thereon so as toprevent or minimize oxidation of the article both during heating andduring any subsequent operations to be performed thereon.

venting or minimizing oxidation thereof during and subsequent to heattreatment.

Another object is to provide an improved method of progressively heatingan article such as a wire or shaft and protecting the same againstoxidation.

Another object is to provide an improved method of heating a metalarticle to the critical temperature and quenching the same, all whileimmersed in a, quenching liquid.

Other objects and various features, of novelty and improvement will behereinafter pointed out or will become apparent to those skilled in theart.

In the drawing which shows; for illustrative P rposes on1y, and more orless diagrammatically. preferred forms of apparatus Fig. l is a view invertical section of apparatus for heat treating an article;

Fig. 2 is a similar view of a modifled'form of apparatus;

Fig. 3 is a vertical sectional view of apparatus 1 for progressivelyheating an .article, such as a shaft or rod; and for coating the articleto prevent oxidation thereof.

In the form shown in Fig. l, I employ a crucible or other container 5 tohold a coating material 6, preferably in the form of a reducingornon-oxidizing salt or other medium, which may be melted and which willserve to coat the metal article immersed therein. I provide means forinductively heating an article, such as a shaft I, which dips into or isimmersed or partially immersed in the coating'material 6. As shown inFig. 1, there may, be an induction heating coil 8 within the contivelyheated article immersed therein. The induction coil 8 may be a greateror less extent act as a resistance heater-to'maintain the coatingmaterial 8 in a liquid condition. The coating material 8 is preferablyof Such a nature that it willadhere to the'surface of the article 8 andIn the preferred form shown in Fig. 1, I provide further inductionmeans, which may be in the form of a separate induction coil lpositionedabove the coil 8 and through which the article I may pass. when the.immersedportion of the article is heated by the induction coil I and thecoating material maintained in a fluid condition, oxidation of thearticle will be prevented by the immersion of the article in anon-oxidizing'coating material. If ahigher degree of heating is coatingbath, say, to the dot-dash line position as shown in Fig. 1, where thearticle with the protective coating adhering thereto may be heat. ed tothe desired temperature by the second induction coil 8. When the articlehas been heated to a point, say, above the critical temperature by thecoil 9, the article may be quickly dropped back into the bath 8 and bethereby quenched. In that connection it will, of course, be understoodthat the bath 6 will be at a temperature sufficiently low to act as aquench when the article has been heated outside of the bath. It will ofcourse be understood that the induction heating means 8-! willordinarily be separately controlled so that the heating is done whenandforth. On the other hand, the bath ll may consist or various othermedia, in some cases even water.

"coll I2 in the form shown in Fig. 2, is not immersed in the bath l Ibut surrounds the container and serves to heat the article II when thelatter ispasseddownintothecoilandimmersedinthe bath H. It wilibeimderstood that the bath II is of a character to be liquid at arelatively low temperature. It may be. used to quench the article II.

The article I: when immersed in the bath u' may, with the properinductioncoil, be very rapidly heated to or above the criticaltemperature even thoughitbeinunersedinthebath. When thearticle issoheated abdve the criticaltemperahire,thecurrentmaybeturnedoflsoastoprevent further heating andthe article maybe then qucnchedin situ bythe bath in which it is imInstead oi immersing the article in a coating Induction heating means,such as the 'of coating material bath, I'may employ other means forcoating the article so as to prevent oxidation thereof, and

in Fig. 3 I have disclosed means for progressively heating and coatingan article which may be a shaft, rod, wire, or the like.

In the form shown in Fig. 3, I provide means for progressively movingthe article H through or past induction heating means, such .as aninduction coil 15. The article will thereby be heated either to thecritical temperature or to such temperature as may be required for anysubsequent operations which it is desired to perform on the article. Atsome point, the article is coated with a coating material so as toprevent oxidation thereof.

I may provide a hopper IE to carry a supply ll, which, for example,might be a salt of the che character above referred to. The hopper hasan outlet tube or spout l8 opening just above the article l4,'and in theform shown positioned so as to drip or flow molten coating material overthe article l4 and between the coils of the induction coil l5. Asillustrated; I employ a small induction coil I9 for heating the tube H8or' the material therein, or both, so as to liquefy the coating materialso it will flow down and thoroughly coat the article l4. When the coil19 is used to heat.

relatively small quantities of the coating material in a more or lesscontinuous manner, a relatively steadyfiow will be maintained eventhough the bulk of the material I"! may remain in the solid state andfall down into the heating zone and be liquefied only as needed.

The heated article, whether heated in the apparatus of the form shown inFigs. 1, 2 or 3, may be subsequently forged or otherwise acted on or maybe quenched. When a non-oxidizin coating is applied to the article, thearticle will not be oxidized during any subsequent operations and thematerial will stay bright and there will be substantially no loss inscale formation if the article be subsequently forged or otherwisetreated. The bath material, as stated, may be of a non-oxidizing andeven of a reducing character. In most cases, a neutral coating servingsimply to exclude air from the surface of the article will sufllce andwill serve to adequately protect the article against oxidation after thecoating is applied. The coating should be such as to adhere quite firmlyso as to protect the metal, but should also be readily removable as bydissolving in water or'other solvent.

While the invention has been described in considerable detail andpreferred method setforth and preferred apparatus more or lessdiaframmatically shown, it is to be understood that various changes maybe made within the scope of the invention as defined --in the appendedclaim.

- the material of the bath forming an oxidation preventing coatingthereon, then inductively heating the coated article, and thereafterreimmersing the article in the bath to quench the same.

DONALD H. MONTGOMERY.

